Not applicable.
Not applicable.
The present invention pertains to pumps and in particular to wobble diaphragm pumps.
Wobble diaphragm pumps, such as those used in air compressors, typically have one or more pistons mounted on a rotatable shaft that is eccentrically driven by a suitable motor to reciprocate each piston in a compression chamber. One type of diaphragm pump has a compliant seal member or diaphragm fixed to the housing at its periphery and attached to the flange of the piston. As the piston reciprocates the diaphragm flexes in and out. Using an appropriate valve assembly, having intake and exhaust valves (such as flapper valves) which alternately open and close during the suction and pump strokes, respectively, the reciprocating motion moves air into and out of the compression chamber.
One problem with ordinary wobble diaphragm pumps is that they can be difficult to assemble. Specifically, the shell of the electric motor unit is often press-fit onto the housing to which the rotor is journaled. Thus, the pistons must be mounted on the shaft by inserting the piston connecting rod down through a hole in the bottom of the compression chamber and angling it as needed to fit a bore in the connecting rod over the shaft. A bearing and an eccentric element must also be mounted onto the shaft and within the connecting rod. This makes it difficult to properly position the connecting rod on the shaft. Failure to properly mount the piston can cause misalignment leading to pump start-up problems, such as motor stall, diaphragm xe2x80x9cslapxe2x80x9d, higher than normal amp draw and shortened operating life.
For conventional piston pumps without diaphragms, piston assembly is made easier by using a housing having an open neck. This allows the assembler to insert the shaft into the housing from the end of the housing and slide the connecting rod through the open neck and onto the shaft until it is seated at the appropriate position on the shaft. Once properly mounted, the open neck can be closed by an end cap fastened to the housing.
While this is suitable for conventional piston pumps, the diaphragm in wobble diaphragm pumps must be held down along its entire circumference to form a seal and create proper pressure differentials. As such, an open necked cylinder would ordinarily leave the diaphragm unsupported at the gap in the neck, and therefore, could not be used in a such a pump.
Accordingly, there is a need for a wobble diaphragm pump that allows for simpler and more accurate assembly.
The present invention solves the problems of the prior art by providing a diaphragm pump with a housing with an open-neck and a separate support ring that closes the open neck and supports the diaphragm about its entire circumference.
In particular, the present invention provides a diaphragm pump having a wobble piston eccentrically mounted to a rotatable shaft at one end and having a compliant sealing member attached at an opposite end. The pump also includes a housing and a support ring. The housing defines a crankcase extending axially beyond the shaft to an open access end and a neck extending perpendicularly to the axis of the shaft. The neck has an open throat which extends to the access end of the crankcase. The open throat allows the piston to be moved axially with respect to the shaft through the throat and onto the shaft. The support ring is mounted to the housing over the throat so as to span the throat and provide a circumferential support surface to which is mounted the circumference of the sealing member.
In a preferred form, the housing and support ring have complimentary locking features for aligning the support ring to the housing. Additionally, the pump includes a valve head mounted to the support ring opposite the sealing member. The support ring and valve head also have complimentary locking features for aligning the valve head to the support ring. The support ring has a stop-gap section that fits within the throat of the housing neck. The stop-gap section is of increased dimension relative to the rest of the support ring and has a convex bottom surface that matches the curvature of the end of the housing. This is provided so that cooling air flow through the housing cannot escape too easily through the throat. The housing also preferably includes a raised wall surrounding a portion of the support ring circumference.
The present invention also provides a method of assembling the diaphragm pump described above. Specifically, the pump is assembled by supporting the shaft inside of the housing crankcase and inserting the piston axially with respect to the shaft through the open throat onto the shaft so that the piston is substantially centered in the neck of the housing. The support ring is mounted on to the housing over the neck so as to span the throat. The sealing member is supported from below about its circumference by the support ring and captured between the support ring and the valve head assembly.
Thus, the present invention provides a diaphragm pump that can be accurately assembled in a simple, cost effective manner. This is accomplished by using an open-neck housing which allows the piston to be slid through the crankcase onto the motor shaft in the proper position. The support ring fills the gap of the throat and provides a circumferential support surface for the sealing member. The accurate piston positioning afforded prevents the occurrence of the aforementioned problems of difficult assembly.
The foregoing and other objects and advantages of the invention will appear from the following description. In this description reference is made to the accompanying drawings which form a part hereof and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference must be made therefore to the claims for interpreting the scope of the invention.